Level shift circuit utilizing resistance in semiconductor substrate

ABSTRACT

A level shift circuit does not affect delay time, regardless of the size of resistor resistance value. The level shift circuit includes first and second series circuits wherein first and second resistors and first and second switching elements are connected in series, rise detector circuits that compare the rise potentials of output signals of the first and second series circuits with a predetermined threshold value, and output first and second output signals, which are pulse outputs of a constant duration, when the threshold value is exceeded, and third and fourth switching elements connected in parallel to the first and second resistors respectively. The gate terminals of the third and fourth switching elements are connected to the rise detector circuits, and the third and fourth switching elements are turned on by the first and second output signals respectively.

TECHNICAL FIELD

The present invention relates to a malfunction prevention method, adelay time shortening method, a current consumption reduction method,and a circuit area reduction method for a level shift circuit typifiedby a half bridge power supply.

BACKGROUND ART

In a half bridge circuit, or the like, in which switching elements areconnected in series and which is driven by a high potential powersupply, a level shift circuit is used in order that a high potentialside switching element is driven by a low potential signal.

FIG. 1 shows a configuration diagram of a half bridge circuit 100 usinga heretofore known level shift circuit. The half bridge circuit 100shown in FIG. 1 is configured of an output circuit 110, a high potentialside drive circuit 120, and a low potential side drive circuit 130. Theoutput circuit 110 is connected to the high potential side drive circuit120 and low potential side drive circuit 130. Also, synchronized signalsare input from the exterior into each of the high potential side drivecircuit 120 and low potential side drive circuit 130.

The output circuit 110 is configured of a switching element XD1, aswitching element XD2, a power source E, and a load L1. In the outputcircuit 110, the switching element XD1 is connected in series to theswitching element XD2, to which the load L1 is connected in parallel,and the high voltage power source E supplies power to the load L1 viathe switching element XD 1. The switching element XD 1 is a highpotential side switching element, and can be, for example, an n-channelor p-channel MOS transistor, a p-type or n-type IGBT (Insulated GateBipolar Transistor), or the like. The switching element XD2 is a lowpotential side switching element, and can be, for example, an n-channelMOS transistor, an n-type IGBT, or the like. Hereafter, the switchingelement XD1 and switching element XD2 will be assumed to be n-channelMOS transistors.

The high potential side drive circuit 120 is configured of a level shiftcircuit, a high side driver 123, and a power source E1 (hereafter, theoutput voltage thereof will also be expressed as E1). The level shiftcircuit is a portion of the high potential side drive circuit 120excluding the high side driver 123 and power source E1, and isconfigured of a latch malfunction protection circuit 121, a latchcircuit 122, a first series circuit 124, a second series circuit 125,feedback resistors R3, R4, R5, and R6 (the resistance values thereof arealso taken to be R3, R4, R5, and R6 respectively), p-channel MOStransistors (hereafter expressed as PM) 1 and PM2, a diode D1 and diodeD2, and an inverter INV.

The first series circuit 124 is configured of a level shift resistor R1(the resistance value thereof is also taken to be R1) and a highbreakdown voltage n-channel MOSFET (hereafter expressed as HVN) 1connected in series, and outputs a level shift output signal setdrn(hereafter expressed as a setdrn signal) to the latch malfunctionprotection circuit 121 via a first connection point Vsetb (the potentialthereof is also taken to be Vsetb). Herein, the first series circuit 124includes a first level shift output terminal (corresponding to the firstconnection point Vsetb) for outputting the setdrn signal to the latchmalfunction protection circuit 121, and the first level shift terminalis connected to the latch malfunction protection circuit 121.

The second series circuit 125 is configured of a level shift resistor R2(the resistance value thereof is also taken to be R2) and an HVN2connected in series, and outputs a level shift output signal resdrn(hereafter expressed as a resdrn signal) to the latch malfunctionprotection circuit 121 via the HVN2 and a second connection point Vrstb(the potential thereof is also taken to be Vrstb). Herein, the secondseries circuit 125 includes a second level shift output terminal(corresponding to the second connection point Vrstb) for outputting theresdrn signal to the latch malfunction protection circuit 121, and thesecond level shift terminal is connected to the latch malfunctionprotection circuit 121.

The PM1 is connected in parallel to the resistor R1 configuring thefirst series circuit 124. The PM2 is connected in parallel to theresistor R2 configuring the second series circuit 125.

A connection point of the feedback resistors R3 and R5 is connected tothe gate terminal of the PM2, and a connection point of the feedbackresistors R4 and R6 is connected to the gate terminal of the PM1. Afeedback circuit is configured of the inverter INV, the feedbackresistors R3, R4, R5, and R6, the PM1, and the PM2. Also, regarding theresistance values of the level shift resistors R1 and R2 and thefeedback resistors R3, R4, R5, and R6, it is taken that R1=R2, R3=R4,and R5=R6.

The setdrn signal and resdrn signal are input into the latch malfunctionprotection circuit 121. The latch malfunction protection circuit 121 isa circuit that, when a false signal called dv/dt noise occurs because ofsource-to-drain parasitic capacitors Cds1 and Cds2 of the HVN1 and HVN2,that is, when the potential Vsetb and the potential Vrstb are both at anL (low) level, outputs at a high impedance so that the latch circuit 122is not affected.

The latch circuit 122 is connected to the latch malfunction protectioncircuit 121 and high side driver 123. The latch circuit 122 is a circuitinto which the output from the latch malfunction protection circuit 121is input that stores and outputs the value of the input when the inputis at an L or H level and, when the input is of a high impedance, holdsand outputs the value stored immediately before the input reaches thehigh impedance.

The output terminal of the latch circuit 122 is connected via thefeedback resistors R4 and R6 to the second connection point Vrstb, whichis a connection point of the level shift resistor R2 and HVN2configuring the second series circuit 125. Also, by inverting the outputof the latch circuit 122 using the inverter INV, an output the inverseof the output of the latch circuit 122 is obtained. The output terminalof the inverter INV that outputs the inverted output is connected viathe feedback resistors R3 and R5 to the first connection point Vsetb,which is a connection point of the level shift resistor R1 and HVN1configuring the first series circuit 124.

The high side driver 123 is connected to the high potential sideswitching element XD1 and latch circuit 122, and outputs a signal HO inaccordance with the output of the latch circuit 122, thereby controllingthe turning on and off of the switching element XD1.

The output terminal of the high side driver 123 is connected to the gateterminal of the switching element XD1. The latch malfunction protectioncircuit 121, the latch circuit 122, the high side driver 123, and thelow potential side power source terminal of the power source E1 areconnected to a connection point vs (hereafter, the potential thereofwill also be expressed as vs) of the switching elements XD1 and XD2.Also, the latch malfunction protection circuit 121, latch circuit 122,and high side driver 123 receive a supply of power from the power sourceE1. In the same way, although not shown, the low potential side powersource terminal of the inverter INV is also connected to the connectionpoint vs, and receives a supply of power from the power source E1.

One end of each of the first series circuit 124 and second seriescircuit 125 is connected to a power source line vb (hereafter, thepotential thereof will also be expressed as vb) connected to the highpotential side terminal of the power source E1, while the other end ofeach is connected to a ground potential (GND). A set signal, which is asignal input into the level shift circuit of the high potential sidedrive circuit 120, is input into the gate of the HVN1, while a resetsignal, which is a signal input into the level shift circuit of the highpotential side drive circuit 120, is input into the gate of the HVN2.

The anodes of the diodes D1 and D2 are connected to the connection pointvs of the switching elements XD1 and XD2, the cathode of the diode D2 isconnected to the first connection point Vsetb, and the cathode of thediode D1 is connected to the second connection point Vrstb. The diodesD1 and D2 are for clamping the voltages Vsetb and Vrstb so that they donot drop to or below the potential vs, thus protecting the latchmalfunction protection circuit 121 by ensuring that no overvoltage isinput.

The feedback resistors R5 and R6 are connected to the vb potential or vspotential via a PMOS or NMOS of a CMOS circuit or logic inversion CMOScircuit (INV) used in the latch circuit 122, but for the sake ofsimplicity, the PMOS and NMOS are not shown in the latch circuit 122,and in the same way, will not be shown hereafter.

The low potential side drive circuit 130 is configured of a low sidedriver 131 that controls the turning on and off of the low potentialside switching element XD2, and a power source E2 (hereafter, thepotential thereof will also be expressed as E2) that supplies power tothe low side driver 131.

The low side driver 131 is supplied with power from the power source E2,amplifies a signal S input into the low side driver 131, and inputs itinto the gate terminal of the switching element XD2. According to thisconfiguration, the switching element XD2 is turned on (energized) whenthe signal S is at an H (high) level, and the switching element XD2 isturned off (cut off) when the signal S is at an L (low) level. That is,the signal S is a signal that directly commands the turning on or off ofthe switching element XD2.

Of the set signal and reset signal input into the high potential sidedrive circuit 120, the set signal is a signal that indicates the timingof the start of an on-state period (the end of an off-state period) ofthe switching element XD1, while the reset signal is a signal thatindicates the timing of the start of an off-state period (the end of anon-state period) of the switching element XD2.

The switching elements XD1 and XD2 are turned on and off in acomplementary way such that when one is in an on-state the other is inan off-state, except during a dead time to be described hereafter, withthe potential vs of the connection point vs reaching the groundpotential when the switching element XD2 is in an on-state, and thepotential vs of the connection point vs reaching the output voltage E ofthe power source E when the switching element XD1 is in an on-state.Also, the load L1 is a load that receives a supply of power from thehalf bridge circuit 100, and is connected between the connection pointvs and the ground potential.

In the kind of heretofore known half bridge circuit 100 shown in FIG. 1,it is often the case that there is a large difference in potential of inthe region of several hundred volts between the low potential side powersource voltage E2 and high potential side power source voltage E1.Because of this, it may happen that the difference in potential occursbetween wiring linking the high potential side circuit and low potentialside circuit and a semiconductor forming an underlay of the wiring. Inparticular, when the wiring potential is a high voltage due to the highpotential side circuit and a subsequent stage is a low potential sidecircuit region, voltage generation and the effect thereof are marked.When simply applying metal wiring of a semiconductor as the wiringlinking the high potential side circuit and low potential side circuit,a high electric field is generated between the wiring and thesemiconductor immediately below, and various problems occur in the levelshift circuit. In order to solve the heretofore described kind ofproblem, it is possible to apply a wire bonding method in the levelshift circuit. A wire bonding method is a method whereby the drain ofthe HVN1 and the first connection point Vsetb, and the drain of the HVN2and the second connection point Vrstb, are connected by wiring in, forexample, FIG. 1. As the wiring is point-to-point wiring distanced fromthe semiconductor when using a wire bonding method, it is possible toprevent a high electric field from being generated in the semiconductorregion forming the underlay.

However, the application of a wire bonding method has a detrimentaleffect on the cost of the level shift circuit and on downsizing theproduct due to, for example, an increase in man-hours, the need forwiring space, and the like. Consequently, there is a demand for a levelshift circuit that does not use a wire bonding method. The technologiesshown in PTL 1 and PTL 2 (identified below) exist as level shiftcircuits that do not use a wire bonding method.

CITATION LIST Patent Literatures

-   PTL 1: Japanese Patent No. 3,941,206-   PTL 2: Japanese Patent No. 3,214,818

A high breakdown voltage IC having a device configuration wherein HVNsare embedded in a high breakdown voltage separation portion (hereafterreferred to as an HVJT), and having parasitic resistors (R1 in FIG. 3 ofPTL 1) configured in parallel with level shift resistors configuring alevel shift circuit, and a technology for controlling the resistancevalue of the parasitic resistors used in the level shift circuit, aredescribed in PTL 1. FIG. 2 shows a configuration of the level shiftcircuit shown in PTL 1. The same reference signs are given to regionsthe same as in FIG. 1, and a detailed description will be omitted. Asshown in FIG. 2, the level shift circuit shown in PTL 1 differs from thelevel shift circuit shown in FIG. 1 in that it includes, in addition tolevel shift resistors LSR1 and LSR2, parasitic resistors LSRp1, LSRp2,and LSRp3. A first series circuit of the parallel resistance of thelevel shift resistor LSR1 and parasitic resistor LSRp1 and the HVN1, anda second series circuit of the parallel resistance of the level shiftresistor LSR2 and parasitic resistor LSRp2 and the HVN2, are configuredin the level shift circuit shown in PTL 1. The resistance values of theparasitic resistor LSRp1 configured in parallel with the level shiftresistor LSR1 and the parasitic resistor LSRp2 configured in parallelwith the resistor LSR2 can be controlled in the level shift circuitshown in PTL 1.

A high voltage power integrated circuit having a device configuration,differing from that in PTL 1, wherein a level shift from a low potentialsignal to a high potential signal is made without using wire bonding,wherein a level shift operation is possible, and that does not have ametal crossover, is described in PTL 2.

The technologies described in PTL 1 and PTL 2 are both such that thecircuit area is reduced by embedding the HVNs in the HVJT region,thereby realizing a high voltage breakdown IC. Also, the kinds of methodshown in PTL 1 and PTL 2 that do not use a wire bonding method differfrom the wire bonding method in terms of device structure in thatparasitic resistors corresponding to the level shift resistors areadded, and that a parasitic resistor is added between the two seriescircuits.

However, the technology described in PTL 1 is such that the first seriescircuit and second series circuit have the same circuit configurationand device configuration. Because of this, a malfunction occurs due tothe drain potentials of the turn-on signal side HVN and turn-off signalside HVN both exceeding the threshold value of a logic circuit at asubsequent stage due to the effect of the current flowing into theparasitic capacitor Cds1 of the HVN1 and the parasitic capacitor Cds2 ofthe HVN2 when dV/dt noise occurs. When reducing the resistance value ofthe level shift resistors in order to avoid this malfunction, thecurrent flowing through the level shift resistors increases when an HVNis turned on and dV/dt noise occurs, and current consumption increases.Also, when the resistance value of the level shift resistors is notreduced, it is necessary to strengthen a noise cancellation functionsuch as a low-pass filter in order to prevent a malfunction caused bylevel shift output fluctuation due to the occurrence of dv/dt noise, andthere is a problem in that delay time increases because of the effect ofthe noise cancellation function.

Also, the technology described in PTL 2 too, in the same way as thetechnology described in PTL 1, is such that the first series circuit andsecond series circuit have the same circuit configuration and deviceconfiguration, because of which there is the problem of malfunction whendV/dt noise occurs, or the like, the problem of power consumptionincreasing due to reducing the resistance value of the level shiftresistors in order to avoid malfunction, and the problem of delay timeincreasing due to strengthening the noise cancellation function when theresistance value of the level shift resistors is not reduced.

Consideration will be given to a case of replacing the level shiftresistors of the heretofore known level shift circuit with the parasiticresistors described in PTL 1 or PTL 2 in order to avoid wire bonding andreduce the circuit area. FIG. 3 shows an example wherein the heretoforeknown level shift circuit shown in FIG. 1 is configured using theHVN-embedded type of HVJT described in PTL 1. The same reference signsare given to regions the same as in FIG. 1, and a detailed descriptionwill be omitted. The main difference between a high potential side drivecircuit 220 of a half bridge circuit 200 shown in FIG. 3 and the highpotential side drive circuit 120 of the half bridge circuit 100 shown inFIG. 1 is the adoption of a configuration wherein the feedback resistorsR3 and R4 are eliminated, the level shift resistor R1 is replaced with aparasitic resistor Rpar1 in the semiconductor substrate, the level shiftresistor R2 is replaced with a parasitic resistor Rpar2 in thesemiconductor substrate, and a parasitic resistor Rpar3 is connectedbetween a first series circuit 221 and second series circuit 222. Thefirst series circuit 221 is configured of the PM1 or parasitic resistorRpar1 and the HVN1, while the second series circuit 222 is configured ofthe PM2 or parasitic resistor Rpar2 and the HVN2. By applying the devicestructure described in PTL 1, PTL 2, and the like in this way, it ispossible to configure a level shift circuit without using wire bondingin the half bridge circuit 200 shown in FIG. 3.

The resistance value of the parasitic resistors varies depending ontemperature, power source voltage, and the like. FIG. 4 shows thetemperature dependency of the parasitic resistor resistance value. Asshown in FIG. 4, the parasitic resistor resistance value is 3 kΩ whenthe temperature is −50° C., while the resistance value is 10 kΩ when thetemperature is 150° C. FIG. 5 shows the power source voltage dependencyof the parasitic resistor resistance value. As shown in FIG. 5, theparasitic resistor resistance value is 3 kΩ when the voltage between thevb and GND is 0V, while the resistance value is 30 kΩ when the voltagebetween the vb and GND is 800V. In this way, the resistance value of theparasitic resistors, which are resistors in the semiconductor substrate,has temperature dependency and power source voltage dependency. Becauseof this, the rise time of the setdrn signal and resdrn signal varies inaccordance with the temperature and power source voltage conditions,which may affect the operation of the level shift circuit, as will bedescribed hereafter.

Also, the resistance value of the parasitic resistor Rpar3 providedbetween the first series circuit 221 and second series circuit 222varies depending on the distance between the HVN1 and HVN2. FIG. 6 showsthe dependency of the parasitic resistor Rpar3 resistance value on thedistance between the HVN1 and HVN2. As shown in FIG. 6, the parasiticresistor Rpar3 resistance value is 500 kΩ when the distance between theHVN1 and HVN2 is 1,000 μm.

In the level shift circuit shown in FIG. 3, the resistance value of theparasitic resistors Rpar1 and Rpar2 is regulated so as to be around 10kΩ, while the resistance value of the parasitic resistor Rpar3 isregulated so as to be around 500M. When the resistance value of theparasitic resistor Rpar3 is on the high side, it is possible to reducethe effect when the level shift circuit carries out each operation.

The half bridge circuit 200 shown in FIG. 3 can change the potential atone end of the feedback resistors R5 and R6 to the vb potential or thevs potential in accordance with the latch circuit 122 output status bychanging the connection status of the feedback resistors R5 and R6 inaccordance with the latch circuit 122 output status. FIG. 7 shows anequivalent circuit diagram of the level shift circuit shown in FIG. 3when an output HO of the high side driver 123 is at an L level, whileFIG. 8 shows an equivalent circuit diagram of the level shift circuitshown in FIG. 3 when the output HO is at an H level. As shown in FIG. 7,when the output HO is at an L level, the parasitic resistor Rpar1 andfeedback resistor R5 are in a condition wherein they are connected inparallel, while the parasitic resistor Rpar2 and feedback resistor R6are in a condition wherein they are connected in series. Consequently,by the gate potential of the PM1 becoming lower than the potential vband the PM1 ceasing to be in a cut off state, the impedance of theoutput terminal of the first series circuit 221 decreases, and by thegate potential of the PM2 becoming the potential vb and the PM1 becomingcut off, the impedance of the output terminal of the second seriescircuit 222 increases. As shown in FIG. 8, when the output HO is at an Hlevel, the parasitic resistor Rpar1 and feedback resistor R5 are in acondition wherein they are connected in series, while the parasiticresistor Rpar2 and feedback resistor R6 are in a condition wherein theyare connected in parallel. Consequently, by the gate potential of thePM1 becoming the potential vb and the PM1 becoming cut off, theimpedance of the output terminal of the first series circuit 221increases, and by the gate potential of the PM2 becoming lower than thepotential vb and the PM1 ceasing to be in a cut off state, the impedanceof the output terminal of the second series circuit 222 decreases.

FIG. 9 shows an operation time chart of the level shift circuit shown inFIG. 3. On the input pulse of the set signal switching to an H level ata time t₁, the setdrn signal drops to the vs potential, and the latchoutput starts to rise to an H level. While the input pulse of the setsignal is at an H level, the setdrn signal continues to be at the vspotential level. On the output of the latch circuit 122 switching froman L level to an H level at a time t₂, the parallel/series condition ofthe feedback resistors R5 and R6 switches. On the input pulse of the setsignal switching from an H level to an L level at a time t₃, the setdrnsignal rises. On the input pulse of the reset signal switching to an Hlevel at a time t₄, the resdrn signal drops to the vs potential, and thelatch output starts to fall to an L level. While the input pulse of thereset signal is at an H level, the resdrn signal continues to be at thevs potential level. On the output of the latch circuit 122 switchingfrom an H level to an L level at a time t₅, the parallel/seriescondition of the feedback resistors R5 and R6 switches. On the inputpulse of the reset signal switching from an H level to an L level at atime t₆, the resdrn signal rises.

When the timing of the inversion (setting) of the output of the latchcircuit 122 is earlier than the input pulse width of the set signal, theimpedance of the output terminal of the first series circuit 221 whenthe setdrn signal starts to rise becomes high, as heretofore described,the time constant of a time constant circuit configured of this and theparasitic capacitor Cds1 increases, and the rise of the setdrn signal isdelayed.

Also, when utilizing the parasitic resistors Rpar1 and Rpar2 as levelshift resistors, the rise time fluctuates due to the effect oftemperature and power source voltage, as heretofore described. As shownin FIG. 4 and FIG. 5, the resistance value of the parasitic resistorsRpar1 and Rpar2 increases when the temperature or voltage rises. Whenthe resistance value of the parasitic resistors Rpar1 and Rpar2increases, the delay in the rise of the setdrn signal and resdrn signalincreases, but provided that the pulses of the set signal and resetsignal are generated singly, there is no problem however long the riseof the setdrn signal and resdrn signal is delayed. However, when theresistance value of the parasitic resistors Rpar1 and Rpar2 is high, thepulse interval between the set signal and reset signal is short, thepulses of the set signal and reset signal are generated continuously,and the next pulse falls before the previous pulse has finished rising,both the setdrn signal and resdrn signal will be at an L level. As dV/dtnoise is generated when both the setdrn signal and resdrn signal are atan L level, it is arranged, in order to combat the generation of dV/dtnoise, that the latch malfunction protection circuit 121 does nottransmit this state to a subsequent circuit. Consequently, as thesubsequent pulse does not become effective until the previous pulse hasfinished rising, the delay time increases, as shown in FIG. 9, andresponsiveness worsens.

FIG. 10 shows circuit simulation results for the half bridge circuit 200shown in FIG. 3 when the pulse interval between the set signal and resetsignal is 0.5 μs. FIG. 11 shows circuit simulation results for the halfbridge circuit 200 shown in FIG. 3 when the pulse interval between theset signal and reset signal is 0.2 μs. As shown in FIG. 10, when thepulse interval between the set signal and reset signal is 0.5 μs, thelatch output waveform shown by the broken line when the parasiticresistor resistance value is 5 kΩ, and the latch output waveform shownby the solid line when the parasitic resistor resistance value is 35 kΩ,are the same.

However, as shown in FIG. 11, when comparing the output waveform whenthe parasitic resistor resistance value is 5 kΩ and the output waveformwhen the parasitic resistor resistance value is 35 kΩ when the pulseinterval between the set signal and reset signal is 0.2 μs, it can beseen that a delay occurs in the latch output waveform when the parasiticresistor resistance value is 35 kΩ.

SUMMARY

The invention provides a level shift circuit that does not affect delaytime, regardless of the size of parasitic resistor resistance value.

In order to solve the heretofore described problem, the inventionaccording to a first aspect is a level shift circuit, characterized byincluding a first series circuit wherein a first resistor in asemiconductor substrate, a first switching element connected to an inputterminal that inputs a first level shift input signal, and a first levelshift output terminal for outputting a first level shift output signalare connected in series, a second series circuit wherein a secondresistor in a semiconductor substrate, a second switching elementconnected to an input terminal that inputs a second level shift inputsignal, and a second level shift output terminal for outputting a secondlevel shift output signal are connected in series, a rise detectorcircuit, connected to the first series circuit and second series circuitand into which are input the first level shift output signal and secondlevel shift output signal output from the first series circuit andsecond series circuit respectively, that compares the rise potential ofthe first level shift output signal and second level shift output signalwith a predetermined threshold value, and outputs a first output signaland second output signal, which are pulse outputs of a constantduration, when the threshold value is exceeded, a third switchingelement connected in parallel to the first resistor, wherein the sourceterminal of the third switching element is connected to a power sourcepotential, the drain terminal of the third switching element isconnected to the first level shift output terminal, and the gateterminal of the third switching element is connected to the risedetector circuit, and a fourth switching element connected in parallelto the second resistor, wherein the source terminal of the fourthswitching element is connected to a power source potential, the drainterminal of the fourth switching element is connected to the secondlevel shift output terminal, and the gate terminal of the fourthswitching element is connected to the rise detector circuit, wherein thethird switching element is turned on by the first output signal from therise detector circuit, and the fourth switching element is turned on bythe second output signal from the rise detector circuit.

The level shift circuit according to a second aspect is the level shiftcircuit according to the first aspect, characterized in that the firstresistor and second resistor are parasitic resistors in thesemiconductor substrate.

The level shift circuit according to a third aspect is the level shiftcircuit according to the first or second aspects, characterized byincluding a logic circuit that outputs a third output signal when eitherof the first output signal or second output signal is output from therise detector circuit, wherein a dead time is provided for the inputtimes of the first level shift input signal and second level shift inputsignal, the output pulse width of the rise detector circuit is equal toor less than the dead time, and the third switching element and fourthswitching element are turned on when the third output signal is output.

The level shift circuit according to a fourth aspect is the level shiftcircuit according to any one of the first to third aspects,characterized by further including a latch malfunction protectioncircuit, into which the first level shift output signal and second levelshift output signal are input, that outputs a high impedance signal whenboth the first level shift output signal and second level shift outputsignal are at an L level, and a latch circuit, into which an output fromthe latch malfunction protection circuit is input, that stores andoutputs the value of the output from the latch malfunction protectioncircuit when the output is at an L or H level and, when the output fromthe latch malfunction protection circuit is of a high impedance, holdsthe value stored immediately before the input reaches the highimpedance, and outputs the stored value together with an inverse signalof the stored value, wherein one output terminal of the latch circuit isconnected via a first feedback resistor to the first level shift outputterminal, and the other output terminal is connected via a secondfeedback resistor to the second level shift output terminal.

The level shift circuit according to a fifth aspect is the level shiftcircuit according to any one of the first to fourth aspects,characterized by further including a first feedback transistor connectedin parallel to the first resistor and a second feedback transistorconnected in parallel to the second resistor, wherein the gate of thefirst feedback transistor is connected to the second level shift outputterminal, and the gate of the second feedback transistor is connected tothe first level shift output terminal.

Advantageous Effects of Invention

According to the invention according to the first aspect, it is possibleto reduce delay time to a minimum, even when using resistors withtemperature characteristics and power source voltage characteristics aslevel shift resistors. Also, it is possible to shorten the pulse inputinterval between a set side pulse input and a reset side pulse input.

According to the invention according to the second aspect, it ispossible to use parasitic resistors with temperature characteristics andpower source voltage characteristics as level shift resistors.

According to the invention according to the third aspect, it is possibleto prevent shoot-through current when the level shift circuit accordingto the first aspect is operating.

According to the invention according to the fourth and fifth aspects, itis possible to prevent malfunction caused by dV/dt noise.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a configuration diagram of a half bridge circuit using aheretofore known level shift circuit.

FIG. 2 shows a configuration diagram of the heretofore known level shiftcircuit.

FIG. 3 shows a circuit configuration diagram when level shift resistorsin the heretofore known level shift circuit configuration are replacedwith parasitic resistors.

FIG. 4 is a diagram showing the temperature dependency of parasiticresistor resistance value.

FIG. 5 is a diagram showing the voltage dependency of parasitic resistorresistance value.

FIG. 6 is a diagram showing the dependency of parasitic resistorresistance value on the distance between HVNs.

FIG. 7 shows an equivalent circuit diagram of the circuit configurationshown in FIG. 3 when a feedback resistor R5 and parasitic resistor Rpar1are in a condition in which they are connected in parallel, while afeedback resistor R6 and parasitic resistor Rpar2 are in a condition inwhich they are connected in series.

FIG. 8 shows an equivalent circuit diagram of the circuit configurationshown in FIG. 3 when the feedback resistor R5 and parasitic resistorRpar1 are in a condition in which they are connected in series, whilethe feedback resistor R6 and parasitic resistor Rpar2 are in a conditionin which they are connected in parallel.

FIG. 9 shows an operation time chart of the level shift circuit shown inFIG. 3.

FIG. 10 is a diagram showing circuit simulation results for the halfbridge circuit 200 shown in FIG. 3 when the pulse interval between theset signal and reset signal is 0.5 μs.

FIG. 11 is a diagram showing circuit simulation results for the halfbridge circuit 200 shown in FIG. 3 when the pulse interval between theset signal and reset signal is 0.2 μs.

FIG. 12 shows a circuit configuration diagram according to Example 1 ofthe invention.

FIG. 13 shows an internal configuration diagram of a rise detectorcircuit.

FIG. 14 shows an operation time chart of the rise detector circuit shownin FIG. 13.

FIG. 15 is a diagram showing another circuit configuration of a risedetector circuit.

FIG. 16 shows an operation time chart of the rise detector circuit shownin FIG. 15.

FIG. 17 is a diagram showing the results of a circuit simulation whenthe pulse interval between a set signal and reset signal is 0.5 μs.

FIG. 18 is a diagram showing the results of a circuit simulation whenthe pulse interval between a set signal and reset signal is 0.2 μs.

FIG. 19 is a diagram showing a circuit configuration of a half bridgecircuit 400 according to Example 2 of the invention.

FIG. 20 is a diagram showing a circuit configuration of a rise detectorcircuit for utilizing the circuit configuration according to Example 2.

FIG. 21 is a diagram showing the relationship between the pulseintervals of a set signal, reset signal, and gen signal and the outputwaveforms of a setdrn signal and resdrn signal.

FIG. 22 is a diagram showing circuit simulation results when the pulseinterval between the set signal and reset signal is 0.5 μs.

FIG. 23 is a diagram showing circuit simulation results when the pulseinterval between the set signal and reset signal is 0.2 μs.

FIG. 24 is a diagram showing a circuit configuration of a half bridgecircuit 500 according to Example 3 of the invention.

FIG. 25 is a diagram showing circuit simulation results when the pulseinterval between the set signal and reset signal is 0.5 μs.

FIG. 26 is a diagram showing circuit simulation results when the pulseinterval between the set signal and reset signal is 0.2 μs.

DETAILED DESCRIPTION Example 1

FIG. 12 is a circuit configuration diagram according to Example 1 of theinvention. The same reference signs are given to regions the same as inFIG. 3, and a detailed description will be omitted. As shown in FIG. 12,a half bridge circuit 300 according to Example 1 of the inventiondiffers from a half bridge circuit 200 shown in FIG. 3 in that thehalf-bridge circuit 300 further includes a PM11, a PM21, a first risedetector circuit 321, and a second rise detector circuit 322. Theresistance values of parasitic resistors Rpar1 and Rpar2 in a highpotential side drive circuit 320 of the half-bridge circuit 300 shown inFIG. 12 can be controlled as described in PTL 1. As one example, theparasitic resistors Rpar1 and Rpar2 at a predetermined power sourcevoltage and predetermined temperature conditions are taken to be of 10kΩ, taking into consideration the temperature characteristics shown inFIG. 4 and power source voltage characteristics shown in FIG. 5. Theresistance value of a parasitic resistor Rpar3 at a predetermined powersource voltage and predetermined temperature, based on the dependency onthe distance between HVN1 and HVN2 shown in FIG. 6, is taken to be the500 kΩ when the distance between HVN1 and HVN2 is 1,000 μm.

The first rise detector circuit 321 is connected to a first seriescircuit 221 and the gate terminal of the PM11, detects a rise of asetdrn signal output from the first series circuit 221, and inputs aset-gen signal into the gate terminal of the PM11. The second risedetector circuit 322 is connected to a second series circuit 222 and thegate terminal of the PM21, detects a rise of a resdrn signal output fromthe second series circuit 222, and inputs a reset-gen signal into thegate terminal of the PM21.

The PM11 is connected in parallel with the parasitic resistor Rpar1 ofthe first series circuit 221, while the PM21 is connected in parallelwith the parasitic resistor Rpar2 of the second series circuit 222. Thegate terminal of the PM11 is connected to the output terminal of thefirst rise detector circuit 321, while the gate terminal of the PM21 isconnected to the output terminal of the second rise detector circuit322.

FIG. 13 is an internal configuration diagram of the first rise detectorcircuit 321 and second rise detector circuit 322. As shown in FIG. 13,the first rise detector circuit 321 and second rise detector circuit 322are configured of a delay circuit 330, a comparator 325, a PMOS gatesignal connection terminal logic circuit 335, and a threshold valuevoltage source E3. The first rise detector circuit 321 differs from thesecond rise detector circuit 322, which inputs the resdrn signal andoutputs the reset-gen signal, only in that it inputs the setdrn signaland outputs the set-gen signal. Hereafter, in order to describe theconfiguration of a rise detector circuit, a description will be givenusing the first rise detector circuit 321 as an example, but the sameoperation is carried out in the second rise detector circuit 322 too,except that the input signals and output signals differ, as heretoforedescribed.

When the setdrn signal is input into the first rise detector circuit321, the setdrn signal is input into the comparator 325 and delaycircuit 330. The comparator 325 is such that the setdrn signal is inputinto one input terminal thereof while a threshold value voltage E3 fromthe threshold value voltage source E3 (the output voltage thereof isalso taken to be E3) is input into the other input terminal, and thecomparator 325 compares the setdrn signal and threshold value voltageE3. The comparator 325 inputs a comparison signal CMO into the PMOS gatesignal connection terminal logic circuit 335, with the comparison signalCMO being at an H level when the signal level of the setdrn signal ishigher than the threshold value voltage, and with the comparison signalCMO being at an L level when the signal level of the setdrn signal islower than the threshold value voltage.

The delay circuit 330 delays the input setdrn signal, and inputs it intothe PMOS gate signal connection terminal logic circuit 335 as a delaysignal DLY. The delay circuit 330 is realized by, for example, a delaycircuit using a method whereby the number of stages of a CMOS logicinverter is changed, a delay circuit wherein a resistive element andcapacitive element are combined, a delay circuit using a method wherebythe parameters of a resistive element and capacitive element arechanged, or the like. The rise detector circuit may be configured sothat, by the comparison signal CMO from the comparator 325 being inputinto the delay circuit 330, the signal CMO rather than the setdrn signalis delayed.

The input terminal of the PMOS gate signal connection terminal logiccircuit 335 into which the delay signal DLY is input is set to have afunction of inverting and inputting the delay signal DLY, while theoutput terminal that outputs the set-gen signal has a function ofinverting the logical product of the comparison signal CMO and theinverted delay signal DLY, and outputting the set-gen signal. That is,the comparison signal CMO and delay signal DLY are input into the PMOSgate signal connection terminal logic circuit 335, the PMOS gate signalconnection terminal logic circuit 335 sets the set-gen signal at an Llevel only when the comparison signal CMO is at an H level and the delaysignal DLY is at an L level, sets the set-gen signal at an H level atall other times, and inputs the set-gen signal into the gate terminal ofthe PM11. In the same way, the second rise detector circuit 322 too,going through the same operation as in the case of the first risedetector circuit 321, but with the resdrn signal as an input, inputs thereset-gen signal into the gate terminal of the PM21.

FIG. 14 shows an operation time chart of the rise detector circuit shownin FIG. 13. As shown in FIG. 14, on the setdrn signal or resdrn signalbeing switched from an H level to an L level at a time t₇, thecomparison signal CMO is also switched from an H level to an L level.The delay signal DLY is switched from an H level to an L level at a timet₈. On the setdrn signal or resdrn signal starting to rise to an Hlevel, the signal level becoming higher than the threshold value voltageE3 at a time t₉, and the comparison signal CMO being switched to an Hlevel, the set-gen signal or reset-gen signal is switched from an Hlevel to an L level. Then, as a PM1 or PM2 is turned on (energized), theset-gen signal or reset-gen signal rises swiftly, and the rise time isshortened. On the delay signal DLY switching to an H level at a timet₁₀, the set-gen signal or reset-gen signal is also switched to an Hlevel.

FIG. 15 shows another circuit configuration of a rise detector circuit.Hereafter, a description will be given using the first rise detectorcircuit 321 as an example. The first rise detector circuit 321 accordingto the other circuit configuration includes the delay circuit 330 andPMOS gate signal connection terminal logic circuit 335. When the setdrnsignal is input into the first rise detector circuit 321, the setdrnsignal is input into the delay circuit 330 and one input terminal of thePMOS gate signal connection terminal logic circuit 335. The delaycircuit 330 delays the input setdrn signal, and inputs it into the otherinput terminal of the PMOS gate signal connection terminal logic circuit335 as the delay signal DLY. As the threshold value of the inputterminals of the PMOS gate signal connection terminal logic circuit 335is a potential intermediate between vb and vs, the PMOS gate signalconnection terminal logic circuit 335 outputs the set-gen signal at an Llevel only when the signal level of the setdrn signal is higher than thethreshold value and the delay signal DLY is at an L level, and outputsthe set-gen signal at an H level at all other times. However, as thethreshold value of the input terminals of the PMOS gate signalconnection terminal logic circuit 335 is a potential intermediatebetween vb and vs, there is a drawback in that the time at which theoutput pulse of the first rise detector circuit 321 changes is delayed,but this drawback is eliminated by lowering the threshold value of the Hlevel side input terminal of the PMOS gate signal connection terminallogic circuit 335.

FIG. 16 shows an operation time chart of the rise detector circuit shownin FIG. 15. As shown in FIG. 16, the setdrn signal or resdrn signal isswitched from an H level to an L level at the time t₇. The delay signalDLY is switched from an H level to an L level at the time t₈. On thesetdrn signal or resdrn signal starting to rise to an H level, and thesignal level becoming higher than the threshold value of the inputterminals of the PMOS gate signal connection terminal logic circuit 335at the time t₉, the set-gen signal or reset-gen signal is switched froman H level to an L level. Then, as the PM1 or PM2 is turned on, theset-gen signal or reset-gen signal rises swiftly, and the rise time isshortened. On the delay signal DLY switching to an H level at the timet₁₀, the set-gen signal or reset-gen signal is also switched to an Hlevel.

FIG. 17 and FIG. 18 show results of the level shift circuit according toExample 1 shown in FIG. 12 being tested by circuit simulation. FIG. 17shows the results of a circuit simulation when the pulse intervalbetween a set signal and reset signal is 0.5 μs. As shown in FIG. 17,even when comparing cases in which the resistance values of theparasitic resistors Rpar1 and Rpar2 are 5 kΩ and 35 kΩ, no delay occursin latch output, which is the same as the simulation results of aheretofore known level shift circuit shown in FIG. 10. FIG. 18 shows theresults of a circuit simulation when the pulse interval between the setsignal and reset signal is 0.2 μs. Despite the fact the a delay occursin the latch output in the simulation results of a heretofore knownlevel shift circuit shown in FIG. 11, no delay occurs in the latchoutput waveform shown in FIG. 18.

Example 2

FIG. 19 is a circuit configuration of a half bridge circuit 400according to Example 2 of the invention. The basic circuit configurationof the half bridge circuit 400 is the same as that in Example 1. Example2 differs from Example 1 in that the configuration is such that thefirst rise detector circuit 321 and second rise detector circuit 322shown in Example 1 are eliminated, one rise detector circuit 421 isprovided instead, the setdrn signal and resdrn signal output from thefirst series circuit 221 and second series circuit 222 are input intothe rise detector circuit 421, and one gen signal output from the risedetector circuit 421 is input into the PM11 and PM21.

FIG. 20 shows a circuit configuration of the rise detector circuit 421for utilizing the circuit configuration according to Example 2. As shownin FIG. 20, the rise detector circuit 421 of a high potential side drivecircuit 420 includes the threshold value voltage source E3, a firstcomparator 435, a first delay circuit 436, a first logical circuit 437,a second comparator 438, a second delay circuit 439, a second logicalcircuit 440, and a PMOS gate signal connection terminal logic circuit441.

The first comparator 435 and first delay circuit 436 are connected tothe first series circuit 221, and the setdrn signal is input into eachof them. The setdrn signal is input into one input terminal of the firstcomparator 435, the threshold value voltage E3 is input into the otherinput terminal, and the first comparator 435 compares the setdrn signaland threshold value voltage E3. The first comparator 435 inputs acomparison signal CMO into the first logic circuit 437, with thecomparison signal CMO being at an H level when the signal level of thesetdrn signal is higher than the threshold value voltage E3, and withthe comparison signal CMO being at an L level when the signal level ofthe setdrn signal is lower than the threshold value voltage E3.

The first delay circuit 436 delays the input setdrn signal, and outputsit to the first logic circuit 437 as a delay signal DLY.

The comparison signal CMO and delay signal DLY are input into the firstlogic circuit 437. The input terminal into which the delay signal DLY isinput is set to have a function of inverting and inputting the delaysignal DLY from the first delay circuit 436, while the output terminalof the first logic circuit 437 has a function of inverting the logicalproduct of the comparison signal CMO from the first comparator 435 andthe inverted delay signal DLY, and outputting a signal.

The second comparator 438 and second delay circuit 439 are connected tothe second series circuit 222, and the resdrn signal is input into eachof them. The resdrn signal is input into one input terminal of thesecond comparator 438, the threshold value voltage E3 is input into theother input terminal, and the second comparator 438 compares the resdrnsignal and threshold value voltage E3. The second comparator 438 inputsa comparison signal CMO into the second logic circuit 440, with thecomparison signal CMO being at an H level when the signal level of theresdrn signal is higher than the threshold value voltage E3, and withthe comparison signal CMO being at an L level when the signal level ofthe resdrn signal is lower than the threshold value voltage E3.

The second delay circuit 439 delays the input resdrn signal, and outputsit to the second logic circuit 440 as a delay signal DLY.

The comparison signal CMO and delay signal DLY are input into the secondlogic circuit 440. The input terminal into which the delay signal DLY isinput is set to have a function of inverting and inputting the delaysignal DLY from the second delay circuit 439, while the output terminalof the second logic circuit 440 has a function of inverting the logicalproduct of the comparison signal CMO from the second comparator 438 andthe inverted delay signal DLY, and outputting a signal.

The PMOS gate signal connection terminal logic circuit 441 inputs a gensignal into the PM11 and PM21, with the gen signal being at an L levelin a case in which an output when the comparison signal CMO of the firstcomparator 435 is at an H level and the delay signal DLY of the seconddelay circuit 436 is at an L level is input from the first logic circuit437, and in a case in which an output when the comparison signal CMO ofthe second comparator 438 is at an H level and the delay signal DLY ofthe second delay circuit 439 is at an L level is input from the secondlogic circuit 440, and with the gen signal being at an H level in allother cases.

When applying the rise detector circuit shown in FIG. 20, a temporalrestriction (a dead time DT) is provided for the set signal and resetsignal.

FIG. 21 shows the relationship between the pulse intervals of the setsignal, reset signal, and gen signal and the output waveforms of thesetdrn signal and resdrn signal. As shown in FIG. 21, on the set signalbeing switched from an L level to an H level at a time t_(a), the setdrnsignal is switched to an L level. On the set signal being switched froman H level to an L level at a time t_(b), the setdrn signal starts torise to an H level, and on the signal level of the setdrn signalbecoming higher than the threshold value voltage E3 at a time t_(c), thegen signal is switched from an H level to an L level. On the delaysignal DLY of the first delay circuit switching to an H level at a timet_(d), the set-gen signal or reset-gen signal is also switched to an Hlevel. On the reset signal being switched from an L level to an H levelat a time t_(e), the resdrn signal is switched to an L level. On thereset signal being switched from an H level to an L level at a timet_(f), the resdrn signal starts to rise to an H level, and on the signallevel of the resdrn signal becoming higher than the threshold valuevoltage E3 at a time t_(g), the gen signal is switched from an H levelto an L level. On the delay signal DLY of the first delay circuitswitching to an H level at a time t_(h), the gen signal is also switchedto an H level.

A dead time period DT is provided for the set signal and reset signal sothat the pulses of the two are not superimposed. That is, unless thedead time period DT has elapsed since the fall of one of the set signalor reset signal, the other signal is not raised. Further, a pulse widthPW of the gen signal of the rise detector circuit 421 is regulated so asto be equal to or less than DT. The pulse width PW of the gen signal canbe regulated by the delay circuit shown in FIG. 20. It is assumed thatthe output amplitude of the gen signal is of a voltage level such that aturning on and off of the PM11 and PM21 is possible.

FIG. 22 and FIG. 23 show circuit simulation results for the level shiftcircuit of FIG. 19. FIG. 22 is the test results when the pulse intervalbetween the set signal and reset signal is 0.5 μs, while FIG. 23 is thetest results when the pulse interval between the set signal and resetsignal is 0.2 μs. As shown in FIG. 22 and FIG. 23, no delay in latchoutput due to a difference in parasitic resistance occurs, even when thepulse intervals differ.

There is an advantage in applying the rise detector circuit 421 shown inFIG. 20 in that, even when a rise of the setdrn signal or resdrn signalis detected, the PM11 and PM21 are turned on, the set-gen signal orreset-gen signal rises swiftly, and the rise time is shortened. Owing toa relative operation of the parasitic resistors Rpar1 and Rpar2 andfeedback resistors R5 and R6, there is no change in an operation wherebyone series circuit is connected in parallel while the other seriescircuit is connected in series, because of which a relationship betweenthe impedances of the first series circuit 221 and second series circuit222 wherein one is low while the other is high is maintained, and arelationship such that no malfunction occurs is maintained.

Example 3

FIG. 24 shows a circuit configuration of a half bridge circuit 500according to Example 3 of the invention. The same reference signs aregiven to regions the same as in FIG. 19, and a detailed description willbe omitted. A high potential side drive circuit 520 of the half bridgecircuit 500 shown in FIG. 24 is such that a first series circuit 521 isconfigured using a series circuit of the parasitic resistor Rpar1 and aparasitic resistor Rpar4, while a second series circuit 522 isconfigured using a series circuit of the parasitic resistor Rpar2 and aparasitic resistor Rpar5. The PM11 and PM21 are connected in parallel tothe parasitic resistor Rpar1 and parasitic resistor Rpar2 respectively.The source terminal of the PM1 is connected to a power source line Vb,while the drain terminal is connected to a first connection point Vsetb,and the gate terminal is connected via a second connection point Vrstband the feedback resistor R6 to the output terminal of a latch circuit122. The source terminal of the PM2 is connected to the power sourceline Vb, while the drain terminal is connected to the second connectionpoint Vrstb, and the gate terminal is connected via the first connectionpoint Vsetb and the feedback resistor R5 to the output terminal of aninverter INV.

FIG. 25 and FIG. 26 show circuit simulation results for the level shiftcircuit shown in FIG. 24. FIG. 25 is the test results when the pulseinterval between the set signal and reset signal is 0.5 μs, while FIG.26 is the test results when the pulse interval between the set signaland reset signal is 0.2 μs. As shown in FIG. 25 and FIG. 26, no delay inlatch output due to a difference in parasitic resistance occurs, evenwhen the pulse intervals differ.

INDUSTRIAL APPLICABILITY

In the description thus far, the Rpar1, Rpar2, Rpar4, and Rpar5 havebeen adopted as parasitic resistors in a semiconductor substrate but,the invention not being limited to parasitic resistance, the normalresistance in a semiconductor substrate may be applied instead of theparasitic resistors Rpar1, Rpar2 and Rpar4. Even when these resistorshave properties in accordance with FIGS. 4 to 6, the effect thereof canbe suppressed by the invention.

The invention claimed is:
 1. A level shift circuit, comprising: a firstseries circuit wherein a first resistor in a semiconductor substrate, afirst switching element connected to an input terminal for inputting afirst level shift input signal, and a first level shift output terminalfor outputting a first level shift output signal are connected inseries; a second series circuit wherein a second resistor in asemiconductor substrate, a second switching element connected to aninput terminal for inputting a second level shift input signal, and asecond level shift output terminal for outputting a second level shiftoutput signal are connected in series; rise detector circuits, connectedto the first series circuit and second series circuit and into which areinput the first level shift output signal and second level shift outputsignal output from the first series circuit and second series circuitrespectively, that compare the rising potential of the first level shiftoutput signal and second level shift output signal with a predeterminedthreshold value, and output a first output signal and second outputsignal, which are pulse outputs of a constant duration, when thethreshold value is exceeded; a third switching element connected inparallel to the first resistor, wherein a source terminal of the thirdswitching element is connected to a power source potential, a drainterminal of the third switching element is connected to the first levelshift output terminal, and a gate terminal of the third switchingelement is connected to the rise detector circuits; and a fourthswitching element connected in parallel to the second resistor, whereina source terminal of the fourth switching element is connected to apower source potential, a drain terminal of the fourth switching elementis connected to the second level shift output terminal, and a gateterminal of the fourth switching element is connected to the risedetector circuits, wherein the third switching element is turned on bythe first output signal from the rise detector circuits, and the fourthswitching element is turned on by the second output signal from the risedetector circuits.
 2. The level shift circuit according to claim 1,wherein the first resistor and second resistor are parasitic resistorsin the semiconductor substrate.
 3. The level shift circuit according toclaim 1, further comprising: a logic circuit that outputs a third outputsignal when either of the first output signal or second output signal isoutput from the rise detector circuits, wherein a dead time is providedfor input times of the first level shift input signal and second levelshift input signal, an output pulse width of the rise detector circuitsis equal to or less than the dead time, and the third switching elementand fourth switching element are turned on when the third output signalis output.
 4. The level shift circuit according to claim 1, furthercomprising: a latch malfunction protection circuit, into which the firstlevel shift output signal and second level shift output signal areinput, that outputs a high impedance signal when both the first levelshift output signal and second level shift output signal are at an Llevel; and a latch circuit, into which an output from the latchmalfunction protection circuit is input, that stores and outputs a valueof the output from the latch malfunction protection circuit when theoutput from the latch malfunction protection circuit is at an L or Hlevel and, when the output from the latch malfunction protection circuitis of a high impedance, holds a value stored immediately before theinput reaches the high impedance, and outputs the stored value togetherwith an inverse signal of the stored value, wherein one output terminalof the latch circuit is connected via a first feedback resistor to thefirst level shift output terminal, and the other output terminal isconnected via a second feedback resistor to the second level shiftoutput terminal.
 5. The level shift circuit according to claim 1,further comprising: a first feedback transistor connected in parallel tothe first resistor and a second feedback transistor connected inparallel to the second resistor, wherein a gate of the first feedbacktransistor is connected to the second level shift output terminal, and agate of the second feedback transistor is connected to the first levelshift output terminal.
 6. The level shift circuit according to claim 2,further comprising: a logic circuit that outputs a third output signalwhen either of the first output signal or second output signal is outputfrom the rise detector circuits, wherein a dead time is provided forinput times of the first level shift input signal and second level shiftinput signal, an output pulse width of the rise detector circuits isequal to or less than the dead time, and the third switching element andfourth switching element are turned on when the third output signal isoutput.
 7. The level shift circuit according to claim 2, furthercomprising: a latch malfunction protection circuit, into which the firstlevel shift output signal and second level shift output signal areinput, that outputs a high impedance signal when both the first levelshift output signal and second level shift output signal are at an Llevel; and a latch circuit, into which an output from the latchmalfunction protection circuit is input, that stores and outputs a valueof the output from the latch malfunction protection circuit when theoutput from the latch malfunction protection circuit is at an L or Hlevel and, when the output from the latch malfunction protection circuitis of a high impedance, holds a value stored immediately before theinput reaches the high impedance, and outputs the stored value togetherwith an inverse signal of the stored value, wherein one output terminalof the latch circuit is connected via a first feedback resistor to thefirst level shift output terminal, and the other output terminal isconnected via a second feedback resistor to the second level shiftoutput terminal.
 8. The level shift circuit according to claim 3,further comprising: a latch malfunction protection circuit, into whichthe first level shift output signal and second level shift output signalare input, that outputs a high impedance signal when both the firstlevel shift output signal and second level shift output signal are at anL level; and a latch circuit, into which an output from the latchmalfunction protection circuit is input, that stores and outputs a valueof the output from the latch malfunction protection circuit when theoutput from the latch malfunction protection circuit is at an L or Hlevel and, when the output from the latch malfunction protection circuitis of a high impedance, holds a value stored immediately before theinput reaches the high impedance, and outputs the stored value togetherwith an inverse signal of the stored value, wherein one output terminalof the latch circuit is connected via a first feedback resistor to thefirst level shift output terminal, and the other output terminal isconnected via a second feedback resistor to the second level shiftoutput terminal.
 9. The level shift circuit according to claim 2,further comprising: a first feedback transistor connected in parallel tothe first resistor and a second feedback transistor connected inparallel to the second resistor, wherein a gate of the first feedbacktransistor is connected to the second level shift output terminal, and agate of the second feedback transistor is connected to the first levelshift output terminal.
 10. The level shift circuit according to claim 3,further comprising: a first feedback transistor connected in parallel tothe first resistor and a second feedback transistor connected inparallel to the second resistor, wherein a gate of the first feedbacktransistor is connected to the second level shift output terminal, and agate of the second feedback transistor is connected to the first levelshift output terminal.
 11. The level shift circuit according to claim 4,further comprising: a first feedback transistor connected in parallel tothe first resistor and a second feedback transistor connected inparallel to the second resistor, wherein a gate of the first feedbacktransistor is connected to the second level shift output terminal, and agate of the second feedback transistor is connected to the first levelshift output terminal.